I have been using a "free" version of SuperDuper! for quite some time to backup both my Mac Mini and Mac Book Air to two external drives, and it works great! In fact, about 2 months ago, it "saved" my bacon, so to speak, on my Mac Mini, as I was able to do a full restore from the most recent SuperDuper! backup taken two days earlier.
The reason I say "free" version is that one can download SuperDuper! and use it for free, but it does lack two things:
1. Scheduled backups.
2. Does not backup the Recovery HD partition.
The paid version does have those features. The lack of Scheduled backups does not bother me, and there is a third party, free product called Recovery Partition Creator that does exactly what it says: create the Recovery partition/software. It's now at version 3.8, but not yet compatible with Yosemite. An update is expected real soon.
I perform cleaning/maintenance/backup processing once a week (usually on Saturdays) for both my Macs. The products I use are Onyx (now at version 2.8.8), TechTool Pro (now at version 7.0.5, and Yosemite compatible), and SuperDuper! (now at version 2.7.3). Such products keep my Macs in good to excellent shape, and of course, I have the bootable backups.